1. Field of the Invention
The present invention relates to a method of and apparatus for establishing a call forwarding service in an electronic switching system, and more particularly to a method of and apparatus for establishing a call forwarding setup with respect to incoming calls from a remote region in an electronic switching system.
2. Description of the Related Art
Japanese patent application laid-open No. 5-284233 discloses a process of applying for call forwarding from an external location with a telephone number for receiving call forwarding requests, and remotely changing a telephone number to which incoming calls are to be forwarded, i.e., the forwarding number, and activating and deactivating call forwarding based on the call forwarding application.
Japanese patent application laid-open No. 5-136910 shows a process of providing a call forwarding service in an ISDN communication system to register a forwarding number based on a call forwarding service registering is made from a remote telephone set to which telephone number an incoming call shall be transferred. The disclosed process allows to register the call forwarding service without recognizing the telephone number to which the incoming call is forwarded.
Japanese patent application No. 63-206055 reveals a process of setting a telephone number to which an incoming call shall be forwarded by verifying a received passward with a password stored in the telephone.
Japanese patent application laid-open No. 2-159154 shows a process of providing relay contacts in a telephone set by which calls are to be forwarded, from a call circuit to an incoming data transfer circuit, and the relay contacts are switched in response to PB tone signals sent from another telephone set.
The process disclosed in Japanese patent application laid-open No. 5-284233 needs a special device for entering a forwarding number and a password from an external location into a telephone set from which incoming calls are to be forwarded, and cannot use ordinary telephone sets.
The process shown in Japanese patent application laid-open No. 5-136910 is limited to devices capable of handling the ISDN communication processing service. This publication does not disclose any verification function.
The process revealed in Japanese patent application laid-open No. 63-206055 requires an ISDN communication unit in both a telephone set from which incoming calls are to be forwarded and a remote telephone set from which a destination number for forwarding is set, and cannot employ general telephone sets.